1. Field of the Invention
The present invention is generally directed to railway rolling stock and more particularly to a system for transporting highway semi-trailers, and the like, by rail.
2. The Prior Art
Systems have heretofore been proposed for moving highway semi-trailers, demountable containers and other types of land moving vehicles by rail on conventional flat cars of sufficient length to support the full length of one or two of such vehicles or containers. Such flat cars have been provided with suitable means to support the highway wheels and suitable fifth wheel assemblies for receipt of the king pin. These systems have numerous disadvantages in that the great overall-height of the flat car and the semi-trailers create clearance problems and provide a vehicle with a very high center of gravity. Also such systems require time consuming and awkward circus-type loading and unloading procedures.
Attempts have been made to lower the overall height of such systems by providing highway wheel pockets in the flat car decks or providing drop-deck flat cars arranged to receive the highway wheels in the center depressed portion. In connection with the latter arrangement, turntables and transfer tables have been provided in the center depressed portions of such flat cars to receive the highway wheels and to permit side loading. Examples of such prior art systems are disclosed in U.S. Pat. Nos. 2,246,543, 2,285,207, 2,782,733, 3,352,438, 3,490,389, 4,129,079, 4,425,064, and 4,516,506.
A system for transporting highway semi-trailers by rail on rail trucks or bogies as the sole support of adjacent rear and front ends of the semi-trailers is disclosed in U.S. Pat. No. 4,179,997, assigned to Intermodal Concepts, Inc. The bogie includes a flat frame structure supported above spaced wheeled axles. A central guideway extends from end to end of the frame structure. A pedestal structure is mounted in the guideway for movement lengthwise thereof substantially from end to end of the frame structure and for supporting a fifth wheel. A pair of highway wheel supporting structures are supported in end to end relation with each other lengthwise on the frame structure. The wheel supporting structures comprise a pair of transversely spaced longitudinally extending treadways, which are transversely spaced apart a sufficient distance so as to receive the pedestal structure between them and permit movement of the fifth wheel to selective positions alternately abreast of the highway wheel supporting structures. The wheel supporting structures accommodate the selective support of the rear highway wheels of a semi-trailer on either of the highway wheel supporting structures and the support of the front king pin of a second highway semi-trailer by the fifth wheel on the end portion of the truck frame carrying the other highway wheel supporting structure.
The system as disclosed in U.S. Pat. No. 4,179,997 has improved upon the prior systems in that it allows for the straddling of a semi-trailer between two bogies or short flat cars, thus permitting the trailer frame rails to distribute longitudinal stress. Also this system provides the ability of transporting both present length trailers and those trailers projected to be of longer length. However, this system has the disadvantage of a great overall height of the flat car and the semi-trailers which creates clearance and increased wind resistance problems. Further, this system has the disadvantage of an awkward, if not dangerous, loading and unloading procedure.